Exam 2 Flashcards
What is the point of no return in the cell cycle?
(if the cell cycle does not finish after this the cell dies)
Transition from G1 to S phase
What does Kinase do?
Uses ATP to phosphorolate Proteins
What is Kinase?
An enzyme
What are Phosphotases
A family of Enzymes
What do phosphotases do?
They remove phosphate groups from proteins
What activates Kinases?
(CDKs)
Cyclin
What are the two roles of Cyclin?
Activate Kinases and give Kinases greater specificity.
When is S-Cyclin and M-Cyclin synthesized?
At the very beginning of S and M phase respectively.
What does the production of S-Cyclin and M-Cyclin do?
Tells the cell to beggin S and M phase respectively.
What does P27 do to activated CDKs?
It deactivates them
What does the S in S phase stand for?
DNA Synthesis
Where does DNA replication start along a chromosome?
Replication Origin Sites
What happens at replication forks?
Parent DNA is unzipped and new DNA is synthesized
How many DNA polymerases per replication fork?
Two
Which direction does DNA polymerase run on the template strand?
3’ to 5’
What direction is new DNA synthesized?
5’ to 3’
What does DNA polymerase need to start making new DNA?
A 3’ OH group called a primer
What does primase do?
Provides primers for DNA polymerase to start replicating
What does topoisomerase do in DNA replication?
Cuts one strand of DNA infront of replication fork to relieve tension
(Ligase fixes the cut)
Approximately how long are okazaki fragments?
200 bp
What are telomeres?
Sequences marking the ends of DNA
In vertebrates - 2500* TTAGGG
What does Telomerase do?
Adds new telomere sequences to the ends of DNA
What are the stages of M phase?
Propase, prometaphase, metaphase, anaphase, and telophase
Is signal induced endocytosis or constitutive endocytosis more common?
Signal induced
Low-density lipoproteins do what?
They transport fat through the blood stream
What makes Low-density lipoproteins unique?
They have a mono layer lipid membrane
How are endosomes similar to the golgi?
They play a role in sorting cell materials
What do lysosomes do?
They degrade unwanted cell materials into the component parts
(monomers)
How much energy is required for protein degredation?
none, degredation is energetically favorable
What does Ubiquitin do?
Marks proteins for degredation by binding to them
How does Ubiquitin bind to proteins?
The Ubiquitin C terminus binds covalently to the amino acid side chains of proteins
What are the names of the enzymes involved in the ubiquitin system?
E1, E2, and E3
Degredation is done in what protein?
Proteasomes
Where are proteasomes found in the cell?
Cytoplasm and Nucleus
What does ESCRT stand for?
Endosomal Sorting Complex Required of Transport
Where are ESCRT proteins found?
The cytoplasmic side of vesicle membranes
What does autophogy do?
delivers large intracelular material to lysosomes for degredation
What are the phases of the cell cycle?
G1, S, G2, M, and division
What do snares do for vesicles?
They pull vesicles to a mebrane through the H2O barrier.
What does the RAB protein do?
It tells the cell where it came form
What typically needs to happen before new proteins can leave the ER?
The protein needs to finish folding
What does glycosylation indicate?
Proteins were synthesized in the ER
What cleaves the N terminus sequence as proteins are built in the ER Lumen?
Signal Peptidase
What are the black dots on the ER?
Ribosomes
What are the three binding sites of ribosomes?
E-site, P-site, and A-site
Where does transcription happen?
nucleus
Where does translation happen?
Cytoplasm
What prtoects the 3’ end of mRNA
the poly A tail
What are exons?
the coding regions of the gene
What does intron splicing do?
signals to export mRNA
Are exons or introns removed to form mature mRNA?
introns
What is the first thing that happens to new RNA?
It gets a 5’ cap
What does the 5’ cap do for RNA?
It helps protect (stabilize) the RNA
Why is RNA so unstable compared to DNA?
RNA doesn’t have protection signals which means the get attacked by RNA cleaving enzymes
What is the base difference in RNA when compared to DNA?
Thymine (DNA) to Uracil (RNA)
What is the sugar difference in RNA when compared to DNA?
deoxyribose (DNA) to ribose (RNA)
What is transcription?
The conversion / copy of DNA to RNA
What direction does transcription run with respect to the coding strand?
5’ to 3’
What are the base pairs in DNA?
A with T (2 hydrogen bonds)
C with G (3 hydrogen bonds)
What is the diameter of DNA?
2 nm
What microtubule does not disassemble very often?
Intermediate filaments
What microtubule is not present in plants or fungi?
Intermediate filaments
What is the diameter of intermediate filaments?
~10 nm
What is the diameter of microtubules?
24 nm
What is the diameter of actin filaments?
8 nm
What is the transport motor for actin?
Myosin
What is the outwards charge in microtubules ?
Positive
Where are new tubulin hetero-dimers added to microtubules?
The positive end
What is the motor that walks to the minus end of tubules?
(inwards)
dynein motor
What motor walks to the plus end of tubules?
(outwards)
Kinesin
What is in the center of mammalian centrosomes?
A pair of centrioles
What changes/defines cellular structure?
Actin filaments
What are the actin modifying proteins?
(there are 9)
Nucleating Protein
Monomer-Sequestering Protein
Severing Protein
Cross-Linking Protein
Capping (plus-end blocking) Protein
Side-Binding Protein
Myosin Motor Protein
Bundling Protein
Branching Protein
How many types of actin are there in the human genome?
six
What is the most abundant intracellulara protein?
Actin
What are the three cytoskeleton filaments?
Actin Filaments
Intramediate Filaments
Microtubules
What ions do muscle cells intake?
Calcium ions
What channels are at the synapse?
Calcium channels
What does the innactivation phase of neurons prevent?
The action potential from running in two directions
What ion rushes into neurons?
Na+ (sodium)
What neuron state is not sensative to membrane potentials?
The inactivated state
Name the types of passive transport?
simple diffusion
channel mediated
transporter mediated
What is the electrochemical gradient?
It is the concentration gradient and membrane potential together
What does the electrochemical gradient determine?
It predicts ion flux
What transports soluable molecules across membranes?
Transporter proteins
What must you know to understand ion flux?
Concentration gradient and membrane potential
What is osmolarity?
The concentration of soluable particles
What allows ion transfer across membranes and exhibits speciificty?
Channels
Do channels or tranport proteins have the ability to move against the gradient?
Transport proteins
What are the three types of lipid movement?
lateral diffusion, flexion, and rotation
what does a more structured lipid membrane mean for the membrane?
A less fluid membrane
What does temperature do to a lipid membrane?
increases fluidity
what do unsaturated fatty acids do to a lipid membrane?
increase fluidity
What does cholesterol do to a lipid membrane?
decreases fluidiity by filling in gaps
Are gel-like or fluid-like membranes thicker?
Gel-like
What does FRAP stand for?
Fluorescence Recovery After Photobleaching
What does FRAP indicate?
Lipid membrane dynamics.
What does a faster FRAP mean?
faster lipid movement
True or False?
Lipid composition of membranes is the same in all organelles.
False
True or False?
The lipid compositon of membranes is adjusted to temperature.
True
True or False?
Lipid membrane composition is adjusted to function.
True
True or False?
Lipid membrane composition is the same on each side of the bi-layer.
False
What are the four membrane associated protein types?
Transmembrane
Monolayer-associated a helix
lipid linked
protein attached
Which of the four membrane associated protein types is salt extractable?
Protein-attached
What do detergents have?
A high CMC
What do detergents do?
Solubilize transmembrane proteins and membranes
What is the most common structure for the transmembrane domain of proteins?
a-helix
What do the hydrophobic side chains of transmembrane protein AA face?
the lipids
Aproximately how long are the transmembrane domains of transmembrane proteins?
~20-25 hydrophobic amino acids
What is a hydrophobicity profile?
The description of how hydrophobic an amino acid is
What does a posative hydrophobicity indicate?
What does a negative hydrophobicity indicate?
Posative - hydrophobic
negative - hydrophilic
What are the functions of transmembrane proteins?
nutrient and ion import/export
structural support
cell signaling/sensing
enzymatic work
True or False?
Water can permeate membranes.
True, but not very fast
What can easily get through membranes?
small, uncharged molecules
What cannot get through membranes?
Ions
What influences membrane permeability?
lipid composition, fluidity, and consistency
What do aquaporins do?
allow for the fast exchange of water but not ions
What is osmolarity?
the total concentration of all solute particles
What is trugor pressure.
the pressure created by water being drawn into the cell
What does turgor pressure do?
It helps maintatin cell structure
What is a concentration gradient?
A higher concentration of molecules on one side of a membrane compared to the other
What is membrane potential?
Unequal charge distribution across the membrane
What do we call the concentration gradient and membrane potential when looked at together?
the electrochemical gradient
What does the electrochemical gradient determine?
Which way charged solutes move across a membrane
What do transporter proteins contain?
a central binding site
What happens when a molecule binds the binding site of a transporter protein?
The protein changes which side is accessable.
What do transporter proteins transport?
molecules and nutrients
True or False?
Channels are just pores.
False
they are pores but they are also selective
Why is glucose considered active transport if movement across the membrane requires no energy?
energy is used to trap the glucose
True or False?
Transport across membranes can be coupled to ion gradients?
True
What gradient is used for nutrient transport in plants and fungi?
proton gradient
What gradient is used for nutrient transport in animal cells?
sodium gradient
How many essential amino acids are there?
8
What are the two ways cells get new amino acids?
through import or synthesis from glucose
Do ion channels allow for water to flow through them?
No
What are the four gating mechanisms of channels?
voltage-gating
ligand-gated (extracellular)
ligand-gated (intracellular)
mechanically-gated
Describe the TRPV1 channel
found in the plasma membrane of neurons, it functions as a pain receptor allowing ions to flux when activated by heat or capsaicin
Are dendrites or axons the long arms on neurons?
axons
Where do neurons recieve information from other neurons?
dendrites
What is action potential?
the rapid and local change of membrane potential propagating along the membrane of neurons
What ion fluxes into the cell causing a membrane potential shift in neurons?
sodium ions
What does a negative membrane potential indicate?
the cytosolic side of the membrane is negative
What is the membrane potential of a resting neuron?
~50mV
What is the membrane potential of an activated neuron?
~40mV
What does the inactivation state of neuron channels ensure?
Action potential directionality
What are the lengths of axons?
less than 1mm to more than 1m
What is the space between the presynaptic nerve terminal and postsynaptic membrane called?
synaptic cleft
What happens when the action potential reaches the end of a neuron?
calcium channels get opened
What are neurotransmitters?
small chemicals used for cell signaling
What does the presenese of calcium do at the end of an axon?
causes the fusion of synaptic vesicles resulting in the release of neurotransmitters
What happens after neurotransmitters are released?
neurotransmitters diffuse across the synaptic cleft binding to an opening a cation channel
What are the three filament types?
actin, microtubules, and intermediate filamnets
Describe actin structure.
twisted two strand 8-9 nm diameter
Describe MT structure.
hollow tube, 24 nm
Describe IF structure.
rope like, 10nm diameter
Where does actin localize?
the edges of the cell
What is the most abundant intracellular protein?
actin
How many forms of actin are encoded in the human genome?
six
What end of actin is the ATP binding site accessible?
the minus end
What is g actin?
the globular monomer form of actin
What is f actin?
actin polymer with structural and functional polarity
What end of F actin is new G actin added?
the plus end
What happens to the ATP on G actin when it binds to F actin?
a phosphate group is lost and it turns into adp
what is the actin motor?
myosin
What does actin sequestering protein do?
keeps actin monomers from polymerizing
What do the proteins fimbrin and filamin do?
cross link actin
How are the proteins fimbrin and filamin different?
fimbrin is small and bundles actin while filamin is long, flexiable, and forms actin networks
What is the cell cortex?
the periphiry region of the cell where actin forms a dense network
True or False?
The cortex is not dynamic.
False
What do actin networks do?
Shape, move, and divide cells
What does the activation of platelets do to the actin network?
actin reorginizes and flattens out the cell
What end does actin polymerize at?
the plus end
What filament is asociated with myosin motors?
actin
What end of actin is oriented towards the plasma membrane?
think about how actin growth and cell growth relate
The posative end
What is the Arp2/3 (ARP) complex?
A protein that forms new actin branches
What end does actin dissasemble at?
the minus end
What are the domains of myosin motors?
The head, neck, and tail domains
What end of myosin binds to the substrate?
tail end
What binds to the head domain of myosin and generates force?
ATPases
What direction do myosin motors walk?
towards the posative end of actin
How much force can an actin motor generate?
3-5pN
How do muscles contract?
myosin motors pull two regions of actin filament together
Where do centrosomes localize?
the perinuclear region
what is a tubulin subunit made of
one alpha + one beta tubulin
In microtubules what tubulin is bound to GTP and which is bound to GDP?
alpha-GTP
beta-GDP
which tubulin hydrolizes the nucleotide?
Beta
Which tubulin represents the plus end of microtubules?
Beta
What are microtubules made of?
protophilaments
what are protophilaments made of?
tubulin dimers
what do protophilaments look like?
lines of tubulin subunits bound minus end to plus end
True or False?
Microtubules are much more rigid than actin.
True
What stabilizes MT ends?
GTP cap
What happens if GTP tublin adds slower to MT than GTP hydrolysis?
MT dissasembles
What end are new tubulin dimers added to the MT?
The plus end
what do gamma tubulin ring complex do?
nucleate MT growth
What is found inside the centrosome?
A pair of centrioles
True or False?
Centrioles are found in all eukaryotes?
False
describe the structure of centrioles?
protohilament triplets aranged into a cylinder
What are the MT motors?
Dynein and Kinesin
What direction does kinesin walk?
The plus end
What direction does dynein walk?
The minus end
True or False?
Microtubules help distibute and localize organelles.
False.
The MT and motors are what do this function
True or False?
The primary cilia is found in almost all mammalian cells.
True
What does the primary cilia do?
mechanical sensing and signaling
What is a basal body?
the nucleating strucutre for MT at the bottom of a cilia
They are centrioles
What causes the flagellum of sperm to move?
dynein motors move MT against each other
What is the flagellum of sperm cells filled with?
Mitochondria
True or False?
Kinesin and Myosin work together for cellular transport at the cell cortex.
True
True or False?
IF are found in all eukaryotes.
False
they are only found in animal cells
What is the main role of IF?
Structural support
Describe the structure of IF.
a-helix monomers dimerize and coil around each other
two dimers form a tetramer
8 tetramers form a IF subunit which add together to form IF
Where are IF found?
all throughout the cytoplasm
What is the nuclear lamina?
Essentially the same as the cell cortex but inside the nucleus and made of IF instead of actin
What carbon is the base of a nucleotide bound to?
the 1’ carbon
What carbon is the phosphate bound to on a nucleotide?
the 5’ carbon
What is the central dogma of molecular biology?
DNA encodes information which is tranfered into RNA which is tranfered into proteins
What is gene expression?
How the information stored in dna is used to produce protein
What is a codon?
three base pairs in sequence
How many codons code for the stop codon?
three
What is the start codon sequence?
ATG
What base changes to what in RNA
T in DNA changes to U in RNA
True or False?
The size of the genome correlates with the number of chromesomes.
False
True or False?
The sum of nuclear DNA is reffered to as the genome?
True
What is eukaryotic DNA packaged into?
chromesomes
How many chromesomes are in the human genome?
2 x 23
When are chromesomes the most compact? When are they the least compact?
Most compact - mitosis
least compact - interphase
What is heterochromatin, where is it, and what does it look like.
dense regions of chromesome, the nucleus, dark spots
True or False?
The outer nuclear membrane is distinct from the ER?
False
they are continuous with one another
What is the space inbetween nuclear membranes called?
the perinuclear space
What size particles can diffuse through nuclear pores?
<60kDa or 9nm
What is the largest particle that can travel through nuclear pores?
26nm
What structure sperates the outer and inner nuclear membrane?
nuclear pores
What does transcription do?
Makes an RNA copy of one strand of DNA
What is RNA a copy of?
the coding strand of DNA
Where is the alcohol group on RNA?
the 2’ carbon
What protein transcribes DNA into RNA?
RNA ploymerase
What is the thing on tRNA which mathces up with the mRNA codon called?
anticodon
True or False?
RNA can have enzymatic functionality.
True
What, upstream of a gene, initiates transcription?
Promoter sequence
What is contained in the promoter sequence?
the TATA box
What does the TATA box do?
recruits general transcription factors
what do general transcription factors do?
recruit RNA polymerase 2
seperate DNA strands
**
What direction does transcription run?
5’ to 3’ of the coding strand
What happens to RNA polymerase before it starts making new RNA?
the RNA tail is phosphorylated
What is the speed of of Transcription?
20-70 bases per second
What is done as soon as the 5’ end of mRNA is accessible?
A 5’ cap is added to the 5’ end of mRNA
What is the poly A tail and where is it found?
a long(100-250 base) chain of adenine added to the 3’ end of mRNA
what are the steps of pre-mRNA processing?
5’ capping
polyA site cleavage
addition of the polyA tail
RNA splicing (removing introns)
what are introns?
non coding regions of a gene that are removed in mRNA processing
what is splicing?
the removal of introns from mRNA
what does mRNA splicing?
spliceosome
What is alternative splicing and how common is it?
different mRNA molecules resulting from the same gene and it is very common (95% of human genome does this)
When does mRNA leave the nucleus?
once it has fully matured
What is translation?
the decoding of mRNA and production of the coresponding protein
What does translation require?
mRNA, ribosomes, and tRNA
True or False?
Ribosomes are among the largest and most abundant protein complexes in cells.
True
What are the subunits of ribosomes?
the large and small subunits
what is the size of the small ribosomal subunit?
40 S
What is the size of the large ribosomal subunit?
60 S
What is the size of the complete ribosomal structure?
80 S
True or False?
RNA is a structural component of ribosomes.
True
What are the three binding sites of ribosomes?
E site, P site, and A site
How can the 30-40 tRNA types cover for all 64 possible codons?
The thrid position in the anticodon can “wobble” or mis-align to form a match
What does tRNA synthetase do?
links the proper amino acid to the proper tRNA
What AA is encoded by ATG(the start codon)
Methionine
What direction does translation happen?
5’ to 3’ of the mRNA
What is the first step of translation?
the small ribosomal subunit with an initiator tRNA scan the mRNA for a start codon
What is the second step of translation?
initiation factors leave the small ribosomal subunit once a start codon is found and the large ribosomal subunit binds
What is the third step of translation?
new tRNA binds the A site of the ribosome and a peptide bond is formed between the two AA
What direction are new proteins synthesized?
N terminus to C terminus
What is the fifth step of translation?
the large subunit moves forward shifting the tRNAs from the P and A sites to the E and P sites respectively
What is the sixth step of translation?
the small subunit shifts forward ejecting the used tRNA from the E site
What terminates translation?
A release factor binds the stop codon causing hydrolysis and the release of the polypeptide form the last tRNA
What is the mRNA and ribosome complex called?
a polysome
True or False?
The protein waits to fold until its polypeptide is completly synthesized?
False
True or False?
Protein folding typically happens in sections which are the protein domains.
True
Do chaperones require energy?
Yes and they use ATP
True or False?
Many proteins require chaperones.
True
What are the functions of the ER?
protein translocation
protein folding
protein glycosylation
protein Quality control
calcium ion storage
what proteins are synthesized at the ER?
transmembrane and translumen proteins
What binds to ribosomes to ensure proper polypeptide insertion into the ER or lumen?
protein translocators
What does SRP stand for and what does it do?
Signal recognition particle
it binds the N terminus of a new polypeptide and directs it to the SRP receptor at the ER
Once the SRP has bound what happens next?
The ribosome binds a translocator and continues polypeptide synthesis
When is the translocator open?
only when ribosomes are bound to them
Once translocation into the ER lumen has begun what happens?
in soluable lumen proteins
the signal sequence is cleaved off
What happens when a transmembrane domain reaches a translocator?
the transmembrane domain is ejected into the ER membrane , the ribosome detatches from the translocator, and polypeptide synthesis continues into the cytoplasm
How do protteins with two or more transmembrane domains get synthesized?
A start transfer sequence tells the ribosome to bind the translocator and synthesize into the lumen
a stop stransfer sequence does the opposite
What is protein glycosylation?
the adition of polysacharides (sugar chains) to AA
Why is glycosylation useful?
It helps the cell recognize foreign vs invader proteins
it also icreases the stability of proteins
True or False?
Only a few proteins at the ER get glycosylated?
False
most proteins are glycosylated
What proteins are allowed to leave the ER?
folded proteins only
Where do newly translated proteins fold?
The ER
What happens if proteins do not fold correctly?
They are kicked out of the ER (using translocators), ubiquinated, and degraded in proteasomes
how do folded ER poteins get to the golgi?
ER budded transport vesicles
How are soluable proteins sorted into vesicles?
by binding receptors
How are transmembrane proteins sorted into vesicles?
by binding coat proteins
After a ER vesicle is formed what happens to it?
it uncoats, tethers the golgi, docks, and fuses with the golgi membrane
What are RAB proteins?
Small GTPases that act as regulators/switches
What determines if a GTPase is on or off?
if it has a bound GTP (on) or a bound GDP (off)
What is the final barrier in vesicle fusion to a membrane and how is it overcome?
The final barrier is a thin film of water
snares break through this barrier
How do snares work?
v snares on the viscle dimerize and twist around t snares on the target membrane thus drawing the vesicle closer to the membrane
What is the main function of the golgi?
protein sorting
which side of the golgi recieves vesicles and what side sends them away?
cis recieves and trans transports away
what are the two secretory pathways?
constitutive secretion and regulated secretion
which secratory pathway do plasma membrane proteins use?
constitutive secretion
Describe how insulin gets released?
Glucose yeilds high ATP which closes potassium channels.
This depolarizes the membrane thus opening calcium channels.
Calcium presense signals the binding of vesicles and release of insulin outside the cell
Where do lots of cell signaling and transport functions localize?
the cell surface
What are eisosomes?
Wrinkles in the cell membrane which store membrane proteins
What is phagocytosis and what cells do it?
the engulfing of large particels (a form of endocytosis)
performed by macrophages
How is phagocytosis done?
the membrane wraps around the object being endocytosed
What is pinocytosis?
the uptake of fluid filled vesicles
~100nm diameter
What are the two types of clathrin and what do they do?
Heavy and Light chain
they assemble into a cage which deformes the membrane
What do adaptors do?
they link cargo recptors or transmembrane proteins and clathrin proteins
What makes LDL interesting?
it has a monolayer membrane
What does LDL transport?
cholesterol and fat
What do early endosomes do?
recieve endocytic vesicles and recycle a portion of the material back to the cell membrane
What is the other name for late endosomes?
Multi Vesicular Bodies (MVB)
What do late endosomes do?
they package membrane and proteins into the lumen and deliver their contents to lysosomes for degredation
What is the function of lysosomes?
degrade macromolecule and store AA and salts
Describe the inside of Lysosomes.
Acidic and full of hydrolytic enzymes
what does protein degredation?
proteases
where are transmembrane proteins degraded?
the lysosome
where are cytoplasmic proteins degraded?
the proteosomes
What is the function of Ubiquitin (UB)?
tag things for degredation
what end of UB binds to the target protein?
the c terminus
True or False?
Only one UB binds to a protein to mark it for degredation.
False
A chain of UB binds to the protein
what does the E1 protein do?
binds free floating UB and prepes it
What does the E2 protein do?
Takes UB from E1 and attaches itself to E3
What does the E3 protein do?
Links the target protein with UB
describe the structure of proteasomes.
A core tube with identical caps on either end
What is used for energy to put UB tagged proteins into proteasomes?
ATP
How does the proteasome work?
the cap unfolds the protein and feed the polypeptide into the core
the core cleaces the protein into small peptides
the opposite cap ejects the degraded material
describe the late endosomal pathway.
a cell surface protein gets ubiquinated and endocytosed in a clathrin coated vesicle
at the late endosome the UB tagged proteins get injested with the help of ESCRTS forming internal vesicles
the late endosome delivers these vesicles to the lysosome
the lysosome degrades its contents
what side are ESCRT proteins found on a membrane
cytoplasmic
on the cell membrane, vesicles, and endosomes
True or False?
ESCRT proteins play a sorting role on late endosomes.
True
Describe the ESCRT mechanism.
No, it is not yet understood how ESCRTs deform away from themselves
Where are late endosomal vesicles and their contents degraded?
the lysosome
what is autophagy?
the degredation of large cellular structures and particles
True or False?
Autophagy is the general term for all organelle degredation.
True, but each organelles degredation has its own name
What induces autophagy?
starvation
Describe the structure of autophagosomes.
double membrane vesicls
How do autophagosomes work?
they encompas their contents and then bind to the lysosomes
what is mitophagy?
the degredation (autophagy) of mitochondria
True or False?
The monmers and degraded material form lysosomes can be reused?
True
What types of cells will continuously divid?
Stem cells
What are the phases of the cell cycle?
G0, G1, S, G2, and M
What happens in the G0 phase?
Differentiation occurs where cells decide if they are stem and will replicate or if they are functional
Generally speaking what controls the cell cycle?
CDKs
What do CDKs do?
phosphorylate (thus regulate) initiation and regulation proteins
What is phosphorylation?
the addition of a phospahte group to something
things are often inactive without a phospahte group on them thus phosphorylation is an activating reaction.
how does cyclin regulate the cell cycle?
Cyclin binds to CDKs activing them
Activated CDKs phosphorylate and thus activate initator/regulatory proteins
those proteins activate phases of the cell cycle
What does degredation of cyclin do?
ensures directionality of the cell cycle and signals the end of a phase
What does the p27 protein do?
inhibits cyclin activated CDKs
How do activated CDKs get inhibited by a kinase?
the kinase adds an inhibtory phosphaate group which is later removed by an activating phosphotase (cdc25)
What are the different ESCRT proteins?
ESCRT-0, ESCRT-I, ESCRT-II, ESCRT-III, Vps4
What is the protein that sreves a checkpoint funtion at spindle assembly?
APC
What protein binds to the kineticor until MT bind and take their place?
Mad2 proteins
What does the release of Mad2 Protein do?
allows for the release of cdc20
What does released cdc20 bind to?
APC
what binds sister chromatids together and gets cut to start anaphase?
cohesin rings
